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What expiry date does NPL state on certificates?

April 26, 2017certificates expiry NPL State

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What expiry date does NPL state on certificates?

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Certified Reference Materials (e.g. Primary Reference Gas Mixtures) produced by NPL under ISO Guide 34 will have an expiry date stated on the certificate [see ISO Guide 34:2000 para 5.9.4]. This is based on NPL’s experience with the stability of the mixture concerned and follows procedures agreed with our external assessment body (UKAS). Calibrations (or ‘certifications’) carried out by NPL (e.g. Calibrated Gas Mixtures) under ISO 17025 do not carry an expiry date on the certificate. This conforms to ISO 17025:2005 [para 5.10.4.4]. The principle advocated by ISO 17025 in this respect is that laboratories using such mixtures should operate a procedure to determine the on-going validity of their standards. Advice on this is included below. Historically, NPL has issued certificates for some gas mixtures that are not covered by accreditation to either ISO Guide 34 or ISO 17025. In these cases NPL has followed one of the approaches described above.